AWWA ACE70897

Manganese interference in the determination of free chlorine using DPD indicator is anon-going problem for analysts in the drinking water industry. This problem will increaseas additional source water supplies are required to comply with the Ground Water Rule.The positive interference caused by manganese often leads to the question, "Is the pinkcolor in my sample really coming from chlorine?" The interference from manganese isnot readily obvious to the analyst because the color forms immediately with the DPDindicator in the same manner as free chlorine. The level of interference can vary fromsample to sample depending upon the relative concentration and reactivity of themanganese present. The impact of the manganese interference is that it will cause anover-estimation of the disinfectant level and microbial protection actually present in thewaters tested. Utilities that are required to monitor free chlorine may not be maintaininga true detectable level throughout all points in their distribution systems. Work has been completed on the evaluation of a new method for determining freechlorine concentrations in the presence of manganese. No pretreatment steps arerequired and the reagents used are not regulated for disposal. The key to thedevelopment of the method was to design a reaction mechanism for free chlorine thatdoes not require the oxidation of an indicator such as DPD. This automaticallyeliminates the oxidant effects of any manganese present in the samples. Analysts donot have to predetermine if manganese is present nor do they need to apply a correctionfactor to compensate for the manganese interference.Results from three utilities comparing the results of this work versus DPD are presented. Includes 3 references, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2009

Number of Pages:

6

File Size:

1 file , 960 KB